PRIOR TO INDUCTION
CAUTION: Obtain informed consent from the subject prior to any of the procedure
1) Ask the subject (if they are getting negative or positive induction) to select one of the two pieces of music:
A) For the negative mood induction: ask subjects to “select the saddest piece of music” and have them listen to both Adagio for strings, Op. 11 by Samuel Barber; Adagio in G Minor by Tomaso Albinoni. Do not name the pieces, simply ask them to select piece 1 or 2.
B) For the positive mood induction: ask subjects to “select the happiest piece of music” and have them listen to both Piano Concerto No. 4, Op. 58 in G Major: III. Rondo: Vivace by Ludwig van Beethoven; Serenade No. 13 KV 525 G-Major: I. Serenade. Allegro by Wolfgang Amadeus Mozart. Do not name the pieces, simply ask them to select piece 1 or 2.
C) For neutral mood induction: this stage can be skipped as asking subjects to choose the most “neutral” piece of music would be ambiguous. They will be played The Planets, Op. 32: VII. Neptune, the Mystic by Gustav Holst
TIMING: Ensure that the subject listens to at least 1 minute of each piece. The pieces of music are, nevertheless, long so allow them to move onto the next piece at any point after a minute. Beyond that, allow them to take as much or as little time (and repeat plays) as they need to make a decision that they are happy with.
TROUBLESHOOTING: This is the best time to ensure that the subjects can hear the music at a comfortable volume: not too quiet that they cannot hear, but not too loud that it is painful. It is helpful if ‘around-ear’ headphones are used because the experimenter should be able to faintly hear the music to confirm that it is playing.
PAUSEPOINT: This can be done any time prior to the induction.
2) Have subjects complete the baseline visual analogue ratings scales (Supplement 1) by making a single vertical mark along each 10cm horizontal line to represent their current mood state.
CRITICAL STEP: This baseline rating scale is a crucial in order to examine the extent of the mood induction by comparison with the post rating scale.
TROUBLESHOOTING: Ask subjects to make a single line (if marking by hand). Sometimes subjects will make an ‘X’ or an ‘O’, which can make it tricky to measure the intercept with the horizontal line.
3) Give detailed instructions to the subject of the mood induction procedure. The standardized script is the same as the instructions which will appear on the screen:
You will now see a series of sentences, each of which will be displayed for 12 seconds before you are given the option to move on. You can then click the next button to continue.
Try to get into the mood suggested by the sentences and relate them to situations in your own life. Feel free to outwardly display the emotions evoked.
The duration of this part of the experiment will be fairly short so you are encouraged to get as deeply into the emotion as possible
4) Ask if the subject needs clarification and answer any questions.
5) Remind the subject that they can stop the experiment at any time.
6) Start the task so that instruction screen loads (see stimulus presentation above)
CRITICAL STEP: Ensure that the task loads the correct piece of music (see stage 1). This music must play for the duration of the experiment, so ensure that it is programmed to loop back to the start once the piece finishes.
7) Tell the subject that they can start the task as soon as they like.
8) After the subject presses the spacebar (or clicks next) the first sentence will then appear on screen. The music should continue from before and the order of sentences should be the same as that used in (Velten 1967). Once each sentence has been displayed for 12 seconds, the ‘next’ button should appear beneath the sentence so the subject knows that they can move onto the next sentence (see figure 2). The sentences should be different in each condition:
A) For the negative mood induction: use the negative Velten sentences (Velten 1967) (e.g.”All the unhappiness of my past life is taking possession of me”)
B) For the positive mood induction: use the positive Velten sentences (Velten 1967) (e.g. “This is great - I really do feel good”)
C) For neutral mood induction: use the neutral Velten sentences (Velten 1967) (e.g. “Agricultural products comprised seventy percent of the income”)
CRITICAL STEP: Each sentence must remain on screen for 12 seconds, during which point the subject should be unable to move onto the next sentence. This is crucial to avoid the subject speeding to the end and reducing the duration of their induction.
TROUBLESHOOTING: Subjects may get impatient and try to skip to the next sentence before the “Next” button appears. As long as the task is programmed to ignore user input until the 12 seconds is complete, they will soon realize that this will not work, so it is not necessary to intervene.
9) Leave the subject alone for the duration of the task. Preferably leave the room to avoid distracting them
TIMING: The task will take at least 12 minutes, but may take longer depending upon how long it takes subjects to move between sentences.
CRITICAL STEP: Music must immediately loop back to the beginning each time it finishes to ensure continuous play.
10) Following the task, have subjects make vertical lines on a second set of visual analogue rating scales (Supplement 1) whilst the music used in the induction continues to play.
CRITICAL STEP: These ratings are the most direct measure of subjective mood state so should be completed as soon as the procedure is finished. Change in mood is measured as a change in ratings from the pre-induction to the post induction rating (see figure 3). Ensure that the music continues during this ratings-scale phase. This can either be programmed as part of the task or, if the computer is needed for something else (e.g. a cognitive task) remember to start the music through another delivery system.
CAUTION: Subjects in the negative mood group may become tearful and upset. It is critical (since this is a mood induction) that no effort be made to comfort the subject (unless they request to end the experiment –in which case do so immediately). If possible explain everything to the subject prior to the induction so that it is not necessary to communicate with the subject until the whole experimental phase is complete (including, if possible, the post induction testing phase). If it is unavoidable for the experimenter to intervene (e.g. to set up testing equipment), then the experimenter should remain neutral at all times and treat all mood induction procedures equally. Do not communicate with the subject more than necessary.
11) Stop the music and have subject complete additional probes (e.g. cognitive task, psychophysiological task, neuroimaging).
TROUBLESHOOTING: Ideally the subject will be pre-trained on these probes so that is not necessary for the experimenter to intervene following the mood induction.
12) Repeat stage 10 rating scales and music as many times as possible at suitable pause points (e.g. between cognitive tasks or between imaging scans)
CRITICAL STEP: The piece of music must be played whilst subjects complete these interim ratings scales. The idea being that the music acts as a ‘booster’ to prolong the mood state. If the subject has removed headphones to complete the probe in stage 11, ensure that the headphones are replaced.
TIMING: Tasks have been completed in this post procedure phase for at least an hour post-induction (Robinson et al. 2010; Robinson et al. 2011a; Robinson et al. 2011b; Robinson and Sahakian 2009a; Robinson and Sahakian 2009b). It is likely that the further this testing phase gets from the initial induction, the weaker the mood effect will be. This decline can be mitigated to a certain extent by the negative music ‘boosters’ during rating scales, but post analysis of these scales can determine whether subjects were still feeling the effects of the induction.
13) At the end of testing, ask the subject for feedback. Provide them with whatever they need to feel better (e.g. ask them how it went, allow them to watch television and/or listen to positive music) and answer any questions they may have. Do not allow them to leave until they feel that their mood state is back to normal. Usually after about 1-1.5 hours following the induction, healthy subjects will not experience any residual effects.